Get set for the comeback of the humble billycart. The gravity powered vehicle which inspired a million motor racing dreams looks set to become the star attraction of a new world series - the Extreme Gravity Racing Series. Extreme Gravity Racing events are currently being staged only in the United States, but the ambitious plan calls for an international series of Extreme Gravity Machines (aka billycarts) racing downhill in beautiful settings around the world - essentially a silent version of Bernie Ecclestone's Formula One circus - the biggest drawcard in international entertainment.